Many human and animal diseases, including cancer, frequently show changes in cellular immunity and in production of lymphokines (nonantibody mediators of cellular immunity). It has been difficult in the past to quantitate these changes with any accuracy in vitro, a difficulty which might be overcome if antibody to a lymphokine associated with cellular immunity were available. Macrophage agglutination factor (MAggF) is a lymphokine produced by antigen-stimulated guinea pig lymph node cells taken from animals with cellular immunity to that antigen. Similar activities have been reported in appropriately stimulated culture supernates of human and animal mononuclear cells. We have determined in the past year that MAggF shares many biochemical and immunochemical properties with fibronectin (FN), a gelatin-binding protein involved in cell adhesion and regulation of cell morphology, and have therefore proposed that MAggF is a form of FN. This project will attempt to isolate MAggF from concentrated culture supernates by sequential use of affinity chromatography over gelatin, gel filtration chromatography and isoelectric focusing. The purified material will be used to raise monoclonal antibodies in mice. The project will also isolate fibronectin, a large gelatin-binding plasma protein with physical, chemical and immunochemical similarities to MAggF, and raise antibodies to it. The specificities of antisera to MAggF and fibronectin will be compared and appropriate antisera then will be used to evaluate the role of MAggF in cellular immunity in vivo and to quantitate it in vitro.